This invention relates to an electrostatic reproduction machine, but more particularly to improvements in a belt tracking system for an endless photoconductor belt of the machine.
In the practice of xerography as described in U.S. Pat. No. 2,297,691 to Chester F. Carlson, a xerographic surface comprising a layer of photoconductive insulating material affixed to a conductive backing is used to support electrostatic images. In the usual method of carrying out the process, the xerographic plate is electrostatically charged uniformly over its surface and then exposed to a light pattern of the image being reproduced to thereby discharge the charge in the areas where light strikes the layer. The undischarged areas of the layer thus form an electrostatic charge pattern in conformity with the configuration of the original light pattern.
The latent electrostatic image may then be developed by contacting it with a finely divided electrostatically attractable material, such as a resinous powder. The powder is held in the image areas by the electrostatic fields on the layer. Where the field is greatest, the greatest amount of material is deposited; and where the field is least, little or no material is deposited. Thus, a powder image is produced in conformity with the light image of the copy being reproduced. The powder is subsequently transferred to a sheet of paper or other surface and suitably fixed to thereby form a permanent print.
The latest machine concept for copiers utilizes high speed flash exposure of a document, and the arrangement of a moving photoconductor material in the form of an endless belt. Photoconductor belts are very delicate, are easily damaged, and the movement thereof through processing stations in the reproduction machine must be accomplished with high precision and with as little irregular movement as possible. Present tracking systems for tracking such belts require very precise machining, and the use of very accurate linkages and ball bearings which both increases the costs and the number of maintenance problems. Thus, what is needed is a reliable low cost tracking system.